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Metabolic Age Calculator

Your metabolic age compares how many calories your body burns at rest (BMR) with what is typical for healthy-weight people of different ages. Enter your details to see whether your metabolism runs younger or older than your years, plus your daily calorie needs.

Last updated:

Sex
years
ft
in
lb
cm
kg
%

From a smart scale or body fat test; makes the estimate reflect muscle

Enter your values to see the result.
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How to use the Metabolic Age Calculator

  1. Select your sex and enter your age.
  2. Enter height and weight in US or metric units.
  3. Choose your activity level to get daily calories.
  4. Optionally add your body fat % from a smart scale for a muscle-aware estimate.
  5. Read your metabolic age and compare it with your real age in the chart and table.

The formulas behind the estimate

  • Mifflin-St Jeor BMR (kcal/day): men = 10 × kg + 6.25 × cm − 5 × age + 5; women = 10 × kg + 6.25 × cm − 5 × age − 161.
  • Katch-McArdle BMR (with body fat %): 370 + 21.6 × lean mass in kg.
  • Size-adjusted BMR = BMR ÷ weight0.75.
  • Reference: the same calculation for a person of your sex and height at BMI 22, for every age.
  • Metabolic age = the age at which the reference value equals yours.

Example: a 40-year-old woman, 165 cm and 63.5 kg (BMI 23.3), has a Mifflin BMR of about 1,305 kcal/day. Divided by 63.50.75 (22.5) that is 58.0, a little below the BMI-22 reference for her age, which gives a metabolic age of about 44.

Activity factors for daily calories

Activity levelDescriptionMultiply BMR by
SedentaryDesk job, little exercise1.2
LightExercise 1–3 days a week1.375
ModerateExercise 3–5 days a week1.55
Very activeHard exercise 6–7 days a week1.725
AthleteTwice-daily training or a physical job1.9

Tips to improve your result

  • Lift weights or do body-weight exercises two or three times a week to build lean mass.
  • Get enough protein to support muscle, especially if you are cutting calories.
  • Walk more during the day; everyday movement adds up even outside workouts.
  • Track the trend every few months rather than reading too much into one number.

Frequently asked questions

What is metabolic age?

Metabolic age is a way of expressing your basal metabolic rate (BMR) as an age. If your resting calorie burn, adjusted for body size, matches that of a typical healthy-weight person aged 35, your metabolic age is 35. It is a motivational estimate, not a medical measurement.

How does this calculator estimate metabolic age?

It calculates your BMR with the Mifflin-St Jeor equation (or Katch-McArdle if you enter body fat %), divides it by weight to the power 0.75 to adjust for body size, and finds the age at which a person of your sex and height at a BMI of 22 has the same value.

Why divide by weight to the power 0.75?

Metabolic rate does not rise in direct proportion to weight; across body sizes it scales roughly with mass to the 0.75 power (Kleiber's law). Using this 'metabolic body size' lets a heavier and a lighter person be compared fairly.

Why is my metabolic age higher than my real age?

Extra body fat burns fewer calories at rest than muscle, so carrying more fat for your height lowers your size-adjusted BMR and raises your metabolic age. Low muscle mass from inactivity has the same effect.

Does activity level change my metabolic age?

Activity does not enter the BMR formulas directly; it is used for your daily calorie needs. But regular strength and endurance training build muscle, which raises BMR. Enter a measured body fat % to let the estimate reflect that muscle.

How can I lower my metabolic age?

Building muscle through resistance training, staying active, reaching a healthier body fat level, eating enough protein and getting good sleep all help. Very low-calorie crash diets can reduce muscle and BMR, which works against you.

Is this the same as a smart scale's metabolic age?

Not exactly. Body composition scales use their own unpublished formulas with bioelectrical impedance readings, so numbers differ between brands. This calculator uses open, published equations so you can see every step.

Are all the tools on FreeToolCabin tested for quality and accuracy?

Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.

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